'A Major Wake-Up Call': What Can The Power Industry Learn From Heathrow's Transformer Explosion?

On March 21, a utility substation transformer near London’s Heathrow Airport exploded. It took officials 18 hours to bring terminals and runways back into operation. Meanwhile, one of the busiest airports in the world experienced unprecedented blackouts, thousands of canceled flights and hundreds of thousands of stranded passengers around the world. 

Transformers change the voltage of alternating current, and if they fail, the electrical grid cannot work. It is estimated that it could cost $100M and take years to install the backup generators needed to prevent this chaos from happening again. But how did it happen in the first place? 

According to Jake Ring, president and co-founder at transformer and high voltage circuit breaker provider Power & Data Management, the fire likely happened due to arc distortion, which leads to arc faults that can cause cumulative insulation damage, winding deformation and accelerated equipment depletion from rapid overheating. Ring is an experienced developer on this equipment and understands how incidents like this occur and, most importantly, the backups needed to keep them from causing catastrophic disruptions. 

Ring spoke with Bisnow about the Heathrow fire and offered his insights into what could be done to prevent disasters like this in the future.  

Bisnow: How does this happen? Can you explain arc distortion? 

Ring: When a utility substation transformer ages beyond its useful life, the transformer is at greater risk to the accumulated exposure of harmonic distortions and their effects to lower winding insulation resistance. Total harmonic distortion values can peak as greater loads with variable speed drives can induce non-sinusoidal current wave forms — like overlapping ripples in a pond after two rocks are dropped close to one another — that cause greater peaks as they overlap, reaching extremely high harmonic levels. At this point, there can be a level of capacitance on the load side such that power on the load side is seeking ground and will find it most easily through the transformer, which causes these low thermal arc faults. 

Arcing activities within the transformer tank, characterized by internal discharges, gradually reduce the dielectric or insulating strength of the transformer’s oil. The arcs strike the paper insulation of the transformer coil windings, leading to fragmentation and a subsequent increase in contaminants. 

Along with the paper fragments reducing the dielectric strength of the insulating oil, it can also induce eddy currents and hysteresis losses in the windings, core and other conductive parts that result in increased temperatures, especially for a transformer that is being tasked at a greater amount of power capacity. This can happen over time and as loads increase the draw on the distribution transformer the overheating can suddenly spike, increasing the pressure inside the transformer such that the insulating oil can burst out and erupt into the blaze witnessed at Heathrow. 

Bisnow: Why didn’t the transformer shut down before it set ablaze?  

Ring: Transformers often fail to shut down before catching fire due to a combination of issues, including near instantaneous failure progression, potentially inadequate safety mechanisms and the nature of electrical and thermal faults. Electrical failures, like short circuits or insulation breakdown, can generate extreme heat — over 2,100°F — and increased gas pressure within milliseconds, overwhelming safety systems before they can shut down.  

For example, a lightning strike can cause sudden, massive voltage surges, and when windings come in contact with each other as insulation breaks down it can result in an internal short circuit. The resulting excessive current flow can cause such overheating in the oil-insulated transformers that the oil breaks down to flammable gases — benzene, acetylene, hydrogen — which can ignite the remaining oil with explosive consequences. 

While transformers do have protective devices in place like pressure relief valves, fuses and even circuit interrupters, these may not respond quickly enough to ultra-fast failures.  

Finally, overloading or environmental stressors like extreme heat or flooding can degrade components like gauges and relays gradually, masking early warning signs.  

Bisnow: Why didn’t a key utility like this have some sort of backup?   

Ring: It would be rare for a utility service like at the Heathrow facility to not to have a backup system. So, we’re left to question whether it too failed. This would be an unprecedented event, especially for critical power infrastructure as it is typically built into grids. Some would call this a major wake-up call for the electric utility industry to prioritize modernization of its equipment. 

Bisnow: Does the industry have standards regarding this type of risk? If so, what are they, and if not, why?  

Ring: The primary federal governing bodies for the United States electric utility industry is the Federal Energy Regulatory Commission, or FERC, which regulates the interstate transmission and wholesale sale of electricity, and the North American Electric Reliability Corporation, or NERC, which is responsible for drafting and enforcing reliability standards for the bulk power system. It is FERC’s job to enforce the standards that NERC develops and proposes that ensure reliable, safe, secure and economically efficient energy. But, it is uncertain whether these standards and compliance, or non-compliance, would have played a role in identifying and addressing the issues experienced with the Heathrow transformer failure. 

There is no single, universally recognized global authority governing the electric utility industry. However, the International Energy Agency serves as a prominent intergovernmental organization providing critical energy policy analysis, data and recommendations that influence the electric utility sector worldwide. 

Bisnow: How is PDM helping usher the industry toward new equipment to mitigate these risks?  

Ring: Power & Data Management started out as a data center developer, so we experienced first-hand the incredible frustrations related to the supply chain crisis back in 2021, specifically with transformers. We would create a project timeline, and it would get blown up because the lead times kept getting pushed out — going from 14 weeks pre-Covid to more than 100 weeks today, in some cases.  

As a result, we decided to leverage our global network from 30-plus years experience at companies like Emerson Electric and General Electric to pivot our business and become an electrical equipment supplier. We developed an exclusive partnership with a manufacturer, and we are now able to offer lead times of nine weeks on padmount transformers and five months on power substation transformers under 250 [megavolt amperes]. 

The company is growing fast, but we’re small enough that when we see potential industry challenges, we can shift gears if needed. For instance, last fall we anticipated the benefits of onshoring some of our production capabilities and opened our first U.S.-based facility in Salt Lake City. This has allowed us to develop a more comprehensive tariff strategy while helping out the local economy with additional employment opportunities. 

This article was produced in collaboration between Power & Data Management and Studio B. Bisnow news staff was not involved in the production of this content.

Studio B is Bisnow’s in-house content and design studio. To learn more about how Studio B can help your team, reach out to studio@bisnow.com.